1. Field of the Invention
The present invention relates to a planar illuminator, and more particularly, to a backlight module with a light source frame having a hollow reflective cavity.
2. Description of the Prior Art
The Liquid Crystal Display (LCD) is the most popular Flat Panel Display (FPD) recently. It has many benefits such as low power consumption, thin shape, light weight, and low driving voltage, etc. Therefore, it is widely applied for many electronic apparatuses, such as the notebook computer, the laptop computer and the television.
Because LCD is not self-illuminated, it needs a backlight module to provide the light source for the image display. Conventionally, the backlight module can be categorized into two types, namely the direct-illumination type and the edge-illumination type. The edge-illumination backlight module is mostly used for the small and medium size LCD, which uses the Cold Cathode Fluorescent Lamp (CCFL) or the Light Emitting Diode (LED) as the light source located at the edge of the backlight module.
FIG. 1 is a cross-sectional schematic diagram of the structure of a conventional edge-illumination backlight module 10. An edge-illumination backlight module 10 is located beneath a LCD panel 20. The edge-illumination backlight module 10 includes: a light source 12; a solid light guide 14; a plurality of optical films 18; and a reflective plate 16. The light emitted from the light source 12 enters into a side surface of the light guide 14, then it is partially guided owing to the internal reflection by the microstructure 142 of the bottom surface 144 of the light guide 14 and partially leaked out from the top surface 146 of the light guide 14, and then penetrates through the optical films 18 to serve as the illumination light for the LCD panel 20.
However, the solid light guide 14 with the microstructure 142 is complex and costly. Furthermore, its weight is heavy such that it is not suitable to be tiled up for the large size display applications.